The invention disclosed and claimed herein relates to an apparatus for recovering solids which are suspended in waste mixture of liquid and solids being evacuated in vacuum drain system. More particularly, the invention is concerned with the extraction of solids contained in a compound liquid waste such as is produced in a dental clinic and carried away by a vacuum drain system connected to one or more drain sources such as sinks.
In the practice of dentistry, compound liquid waste, comprising water, chemicals, metal particles, and soap emulsion, is produced from such activities as hand washing, dental surgery, dental maintenance, and dental chemistry. The waste is disposed of through sinks and cuspidors in a dental clinic. To complete the disposal, most dental offices now use vacuum-assisted waste disposal systems which collect and process the waste and carry it to a sewage drain.
The compound liquid waste is collected and processed in order to extract and salvage some of the solid materials, such as gold and silver, which are suspended in it. It is also desirable to extract as much of the rest of the solid material as possible in order to prevent it from clogging either the drain system, the sewage system, or both.
The art shows a number of existing vacuum drain systems which separate solid waste from a mixture of liquid and suspended solids. An example of a vacuum-assisted liquid waste disposal system which separates solids from the waste is found in the A-dec Systems Guide which lists and describes equipment available from A-dec, Inc., Newberg, Oreg. In the A-dec vacuum drain actuator assembly, liquid waste compound flows from a cuspidor or sink drain into a chamber. A vacuum microvalve is adapted to sense the total mass of the waste in the chamber. While the liquid waste compound accumulates in the chamber, the solids suspended therein settle out through an opening in the bottom of the chamber to a solids collector jar. When the microvalve senses that a given amount of liquid waste compound has accumulated in the drain chamber, it sends a pneumatic signal to a vacuum-operated drain valve which causes the drain valve to open, allowing the remaining liquid to flow out of the chamber. As the level of liquid in the drain chamber falls, the microvalve changes state and closes the drain valve so that more waste compound can enter the chamber to be separated into its liquid and solid components.
While the A-dec assembly is efficient in separating solids from the liquid waste, it depends for its operation on an expensive, precision pneumatic control and valve assembly. Both the microvalve and the air controlled drain valve are susceptible to being jammed by the solids suspended in the liquid waste compound and are difficult to repair and maintain. Also, the interconnection of the control and valve assembly by an air hose network increases the chance of a system malfunction which can result from damage to one of the hoses. Moreover, the assembly provides no indication of the amount of solids collected, which would be useful in signalling an operator to change or empty the solids collection jar. Finally, if the vacuum system fails to operate while waste continues to accumulate in the assembly, eventually the waste will back up the drain and overflow the basin.
For the foregoing reasons it is highly desirable that an on-line solids collecting means be provided for extracting the solid material from compound liquid waste being evacuated in a vacuum drain system, and that such solids collecting means be characterized by having in simple arrangement few moving parts which are actuated by simple techniques, which require no adjustment, and which are easily repaired. In addition, it would be convenient to an operator if such a means provided an indication when the amount of solids removed exceeded a predetermined level so that the operator could take action to remove the collected solids. Further, it would be desirable for such a solids collecting means to be able to continue to drain waste from a sink even in the event of a failure of the vacuum.